two_percent 0.10.20

use crate::global::mark_new_run;
///! Reader is used for reading items from datasource (e.g. stdin or command output)
///!
///! After reading in a line, reader will save an item into the pool(items)
use crate::options::SkimOptions;
use crate::spinlock::SpinLock;
use crate::{SkimItem, SkimItemReceiver};
use crossbeam_channel::{bounded, Select, Sender};
use std::cell::RefCell;
use std::rc::Rc;
use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
use std::sync::{Arc, Weak};
use std::thread::{self, JoinHandle};

const CHANNEL_SIZE: usize = 1024;
const ITEMS_INITIAL_CAPACITY: usize = 65536;

pub trait CommandCollector {
    /// execute the `cmd` and produce a
    /// - skim item producer
    /// - a channel sender, any message send would mean to terminate the `cmd` process (for now).
    ///
    /// Internally, the command collector may start several threads(components), the collector
    /// should add `1` on every thread creation and sub `1` on thread termination. reader would use
    /// this information to determine whether the collector had stopped or not.
    fn invoke(
        &mut self,
        cmd: &str,
        components_to_stop: Arc<AtomicUsize>,
    ) -> (SkimItemReceiver, Sender<i32>, Option<JoinHandle<()>>);
}

pub struct ReaderControl {
    tx_interrupt: Sender<i32>,
    tx_interrupt_cmd: Option<Sender<i32>>,
    components_to_stop: Arc<AtomicUsize>,
    items: Arc<SpinLock<Vec<Arc<dyn SkimItem>>>>,
    thread_reader: Option<JoinHandle<()>>,
    thread_ingest: Option<JoinHandle<()>>,
}

impl Drop for ReaderControl {
    fn drop(&mut self) {
        self.kill();
        self.items.lock();
    }
}

impl ReaderControl {
    pub fn kill(&mut self) {
        debug!(
            "kill reader, components before: {}",
            self.components_to_stop.load(Ordering::SeqCst)
        );

        let _ = self.tx_interrupt_cmd.as_ref().map(|tx| tx.send(1));
        let _ = self.tx_interrupt.send(1);

        if let Some(handle) = self.thread_reader.take() {
            let _ = handle.join();
        }
        if let Some(handle) = self.thread_ingest.take() {
            let _ = handle.join();
        }

        while self.components_to_stop.load(Ordering::SeqCst) != 0 {}
    }

    pub fn take(&self) -> Vec<Arc<dyn SkimItem>> {
        let mut locked = self.items.lock();

        std::mem::take(&mut *locked)
    }

    pub fn is_done(&self) -> bool {
        let locked = self.items.lock();
        self.components_to_stop.load(Ordering::SeqCst) == 0 && locked.is_empty()
    }
}

pub struct Reader {
    cmd_collector: Rc<RefCell<dyn CommandCollector>>,
    rx_item: Option<SkimItemReceiver>,
}

impl Reader {
    pub fn with_options(options: &SkimOptions) -> Self {
        Self {
            cmd_collector: options.cmd_collector.clone(),
            rx_item: None,
        }
    }

    pub fn source(mut self, rx_item: Option<SkimItemReceiver>) -> Self {
        self.rx_item = rx_item;
        self
    }

    pub fn run(&mut self, cmd: &str) -> ReaderControl {
        mark_new_run(cmd);

        let components_to_stop: Arc<AtomicUsize> = Arc::new(AtomicUsize::new(0));
        let items_strong = Arc::new(SpinLock::new(Vec::with_capacity(ITEMS_INITIAL_CAPACITY)));
        let items_weak = Arc::downgrade(&items_strong);

        let (rx_item, tx_interrupt_cmd, opt_ingest_handle) =
            self.rx_item.take().map(|rx| (rx, None, None)).unwrap_or_else(|| {
                let components_to_stop_clone = components_to_stop.clone();
                let (rx_item, tx_interrupt_cmd, opt_ingest_handle) =
                    self.cmd_collector.borrow_mut().invoke(cmd, components_to_stop_clone);
                (rx_item, Some(tx_interrupt_cmd), opt_ingest_handle)
            });

        let components_to_stop_clone = components_to_stop.clone();
        let (tx_interrupt, thread_reader) = collect_item(components_to_stop_clone, rx_item, items_weak);

        ReaderControl {
            tx_interrupt,
            tx_interrupt_cmd,
            components_to_stop,
            items: items_strong,
            thread_reader: Some(thread_reader),
            thread_ingest: opt_ingest_handle,
        }
    }
}

fn collect_item(
    components_to_stop: Arc<AtomicUsize>,
    rx_item: SkimItemReceiver,
    items_weak: Weak<SpinLock<Vec<Arc<dyn SkimItem>>>>,
) -> (Sender<i32>, JoinHandle<()>) {
    let (tx_interrupt, rx_interrupt) = bounded(CHANNEL_SIZE);

    let started = Arc::new(AtomicBool::new(false));
    let started_clone = started.clone();
    let thread_reader = thread::spawn(move || {
        debug!("reader: collect_item start");
        components_to_stop.fetch_add(1, Ordering::SeqCst);
        started_clone.store(true, Ordering::SeqCst); // notify parent that it is started

        let mut sel = Select::new();
        let item_channel = sel.recv(&rx_item);
        let interrupt_channel = sel.recv(&rx_interrupt);

        if let Some(items_strong) = items_weak.upgrade() {
            'outer: loop {
                match sel.ready() {
                    i if i == item_channel => {
                        let mut locked = items_strong.lock();

                        'inner: for _ in 0..256 {
                            match rx_item.try_recv() {
                                Ok(item) => {
                                    locked.push(item)
                                }
                                Err(err) => {
                                    if err.is_disconnected() {
                                        break 'outer;
                                    }

                                    if err.is_empty() {
                                        break 'inner;
                                    }
                                },
                            }
                        }
                    },
                    i if i == interrupt_channel => break 'outer,
                    _ => unreachable!(),
                }
            }
        }

        components_to_stop.fetch_sub(1, Ordering::SeqCst);
        debug!("reader: collect_item stop");
    });

    while !started.load(Ordering::SeqCst) {
        // busy waiting for the thread to start. (components_to_stop is added)
    }

    (tx_interrupt, thread_reader)
}